System and Method for Rendering Virtual Contaminants

ABSTRACT

A method and a computer system for performing a computer simulation in which virtual contaminants are rendered on a rendered scene of the computer simulation. A memory module is sued for loading thereinto a model defining a virtual environment of the computer simulation, the virtual environment defining a plurality of zones comprising a first additive zone and a second subtractive zone, the second subtractive zone being at least partially enclosed within the first additive zone. An image generator module is used for adding a virtual contaminant over the first additive zone, removing, at least partially, the virtual contaminant within the second subtractive zone leaving a remaining virtual contaminant in the first additive zone and rendering an image for display comprising the remaining virtual contaminant in the virtual environment using a visual texture of the virtual contaminant. The computer simulation may be a vehicle computer simulation.

TECHNICAL FIELD

The present invention relates to computer generated images and, moreparticularly, to generating images using a computer based on a modeledenvironment.

BACKGROUND

In computer simulation, an important aspect is to credibly replicate anactual environment where various conditions may be set and/or adjusted(e.g., atmospheric conditions, ground conditions, etc.). In order toremain credible, the rate of image generation in the computer simulationhas to remain high enough to be seen as fluid from the user perspective.However, the computer generated images necessary for the computersimulation to be credible typically require a lot of material resources(e.g., processing power, memory and/storage space, etc.). Consequently,it is often necessary to let go of some level of environmentalreplication to remain within accessible material resources.

The present invention aims at improving the level of environmentalreplication while providing a solution that takes into considerationusage of the material resources.

SUMMARY

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

A first aspect of the present invention in accordance with a first setof embodiments is directed to a method for rendering virtualcontaminants on a rendered scene in a computer simulation. The methodcomprises reading a model from a database. The model defines a virtualenvironment of the computer simulation. The virtual environment definesa plurality of zones comprising a first additive zone and a secondsubtractive zone, the second subtractive zone being at least partiallyenclosed within the first additive zone, The method further comprisesadding a virtual contaminant over the first additive zone, removing, atleast partially, the virtual contaminant within the second subtractivezone leaving a remaining virtual contaminant in the first additive zoneand rendering an image for display comprising the remaining virtualcontaminant in the virtual environment using a visual texture of thevirtual contaminant.

The computer simulation may be a vehicle computer simulation and a fieldof view for rendering the image may be defined from a user's positionwithin a simulated vehicle. In that context, the method may furthercomprise receiving control command inputs from an input instrumentsimulation module, computing the control command inputs in accordancewith rules of the computer simulation and, in response to the computing,modifying the field of view for rendering a subsequent image for displaycomprising the remaining virtual contaminant in the virtual environment.

Removing, at least partially, the virtual contaminant may optionally beperformed, during the computer simulation, before each time imagerendering for display is performed. Adding the virtual contaminant may,as a complementary option, be performed, during the computer simulation,before each time removing, at least partially, the virtual contaminantis performed. Adding the virtual contaminant may alternatively beperformed for the rendered scene at once, before rendering the image fordisplay is performed during the computer simulation. Rendering the imagefor display may optionally be performed in an image generator modulehaving one or more dedicated graphical processing units.

In another optional embodiment, adding the virtual contaminant andremoving, at least partially, the virtual contaminant may be performedfor the rendered scene at once, before rendering the image for displayis performed during the computer simulation.

The virtual environment may further define a plurality of additivepolygons within the first additive zone. Adding the virtual contaminantwould then further comprise performing a maximum mathematical operationon the plurality of additive polygons to obtain a virtual contaminantimage mask for the first additive zone. The virtual environment may alsooptionally define a plurality of subtractive polygons within the secondsubtractive zone.

The plurality of additive polygons may further comprise linear polygonsassociated with a single pre-defined texture, tip polygons associatedwith two pre-defined textures and custom polygons associated with aplurality of arbitrary textures.

Removing the virtual contaminant may further comprise, during thecomputer simulation and before each time image rendering for display isperformed, performing a minimum mathematical operation on the pluralityof subtractive polygons to obtain the remaining virtual contaminant inthe virtual contaminant image mask for the first additive zone.Rendering the image for display may thus comprise rendering theremaining virtual contaminant in the virtual contaminant image mask byperforming a multiply mathematical operation on the visual texture ofthe virtual contaminant and the virtual contaminant image mask. Thevisual texture of the virtual contaminant may further be mapped onto theplurality of additive polygons.

In an optional embodiment, the virtual environment may define pathswithin at least the second subtractive zone using vectors and removingthe virtual contaminant may then be performed by extrusion along thepaths. The extrusion may be performed in 2D along the paths and thepaths may define at least one border for allowing smooth visualtransition with one or more images neighboring the paths.

A second aspect of the present invention in accordance with the firstset of embodiments is directed to a computer system for performing acomputer simulation in which virtual contaminants are rendered on arendered scene of the computer simulation. The computer system comprisesa memory module for loading thereinto a model defining a virtualenvironment of the computer simulation. The virtual environment definesa plurality of zones comprising a first additive zone and a secondsubtractive zone, the second subtractive zone being at least partiallyenclosed within the first additive zone. The computer system alsocomprises an image generator module for adding a virtual contaminantover the first additive zone; removing, at least partially, the virtualcontaminant within the second subtractive zone leaving a remainingvirtual contaminant in the first additive zone and rendering an imagefor display comprising the remaining virtual contaminant in the virtualenvironment using a visual texture of the virtual contaminant.

The computer simulation may be a vehicle computer simulation and a fieldof view for rendering the image is defined from a user's position withina simulated vehicle. In that context, the computer system may furthercomprise an input instrument simulation module for receiving controlcommand inputs and a simulation computing module for computing thecontrol command inputs in accordance with rules of the computersimulation. The image generator module may, in response to thecomputing, further modify the field of view for rendering a subsequentimage for display comprising the remaining virtual contaminant in thevirtual environment.

The image generator module may remove, at least partially, the virtualcontaminant during the computer simulation, before each time imagerendering for display is performed. The image generator module may alsoadd the virtual contaminant during the computer simulation, before eachtime removing, at least partially, the virtual contaminant is performed.Alternatively, the image generator module may add the virtualcontaminant for the rendered scene at once, before rendering the imagefor display is performed during the computer simulation. The imagegenerator module may also comprise one or more dedicated graphicalprocessing units.

In another optional embodiment, the image generator module may add thevirtual contaminant and may remove, at least partially, the virtualcontaminant for the rendered scene at once, before rendering the imagefor display being performed during the computer simulation.

The virtual environment may further define a plurality of additivepolygons within the first additive zone and the image generator modulemay then add the virtual contaminant by performing a maximummathematical operation on the plurality of additive polygons to obtain avirtual contaminant image mask for the first additive zone.

The plurality of additive polygons may further comprises linear polygonsassociated with a single pre-defined texture, tip polygons associatedwith two pre-defined textures and custom polygons associated with aplurality of arbitrary textures.

The virtual environment may also define a plurality of subtractivepolygons within the second subtractive zone and the image generatormodule may then remove the virtual contaminant by performing a minimummathematical operation on the plurality of subtractive polygons toobtain the remaining virtual contaminant in the virtual contaminantimage mask for the first additive zone. The image generator module mayfurther render the image for display by rendering the remaining virtualcontaminant in the virtual contaminant image mask by performing amultiply mathematical operation on the visual texture of the virtualcontaminant and the virtual contaminant image mask. The visual textureof the virtual contaminant may further be mapped onto the plurality ofadditive polygons.

In an optional embodiment, the virtual environment may define pathswithin at least the second subtractive zone using vectors and the imagegenerator module may then remove the virtual contaminant by extrusionalong the paths. The extrusion may be performed in 2D along the pathsand the paths may further define at least one border for allowing smoothvisual transition with one or more images neighboring the paths.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and exemplary advantages of the present invention willbecome apparent from the following detailed description, taken inconjunction with the appended drawings, in which:

FIG. 1 is a logical representation of an exemplary computer system inaccordance with the teachings of the present invention;

FIG. 2 is a flow chart of an exemplary rendering method in accordancewith a first set of embodiments of the present invention; and

FIG. 3 is a flow chart of an exemplary modeling method in accordancewith a second set of embodiments of the present invention.

DETAILED DESCRIPTION

Reference is now made to the drawings in which FIG. 1 shows a logicalrepresentation of an exemplary computer system 1200 in accordance withthe teachings of the present invention. FIG. 1 also shows a logicalrepresentation of an optional network 1300 that may be used in certainembodiments of the present invention. The computer system 1200 comprisesa memory module 1220 and a processor module 1230. A display device isprovided with the computer system 1100A and/or in communication with thecomputer system 1100B (both solutions being referred to as 1100). Thedisplay device 1100 may comprise at least one physical display unit, andmay also comprise many display units of one or more technologies (e.g.,Cathode Ray Tube (CRT), Liquid Crystal Display (LCD) screen orprojector, any means to project the image onto a screen, mirror and/ordisplay surface, etc.). A storage module is provided with the computersystem 1400A and/or in communication with the computer system 1400B(both solutions being referred to in the description as 1400). Thestorage devices module 1400A and/or 1400B may represent one or morelogical or physical as well as local or remote hard disk drive (HDD) (oran array thereof). The storage devices module 1400 may further representa local or remote database made accessible to the computer system 1200by a standardized or proprietary interface. The computer system 1200may, in certain embodiments, comprise a network interface module 1210and an instrument simulation module 1250. The processor module mayfurther comprise, or may be seen logically as comprising, an imagegenerator module 1232 and a simulation computing module 1234. The imagegenerator module 1232 may also comprise one or more dedicated graphicalprocessing units.

The network interface module 1210, e.g., through one or more of itsinterfaces (e.g., 1212, 1214, 1216), may be used in the context of thepresent invention to communicate through the network 1300 with thedisplay device 1100B (e.g., display data over Ethernet) and/or with thestorage module 1400B (e.g., to store and/or load a model of a computersimulation). The one or more interfaces may use different protocols andphysical medium (e.g., local area network (LAN) over twisted paircables, wireless LAN, wide area network (WAN) over cable, optical fiber,cellular, etc.), metropolitan area network MAN), etc.).

Virtual contaminants (or virtual contaminant) may represent snow on theground, ice, dirt, water, mud, loose leafs, etc. The virtualcontaminants may be defined as a 2D image in the 3D virtual environment,but may also represent a 3D shape having a 2D projected image in the 3Dvirtual environment.

The computer simulation may, for instance, be used for training purposesand/or for enacting a scenario from historical data (e.g. from an eventrecording device (e.g., black box) from an aircraft, a train, etc.). Thecomputer simulation may be scenario-based (e.g., where simulation codedriving the simulated environment comprises one or more predeterminedevents, motions, sounds, etc.).

The computer simulation may be a vehicle computer simulation and a fieldof view for rendering the image may be defined from a user's positionwithin a simulated vehicle. The present invention is not limited by thetype of simulated vehicle, which may be terrestrial (car, tank, etc.),underground, airborne (e.g., an aircraft, a space shuttle), floating(e.g., a boat), etc. The field of view, or point of view, may be definedfrom the position of a trainee of the simulated vehicle (e.g.,interacting with the simulation) and/or the position of an operator ofthe simulated vehicle (e.g., only determining content of the simulationcode or participating to the simulation as well).

In accordance with a first set of embodiments, the computer system 1200performs a computer simulation in which virtual contaminants arerendered on a rendered scene of the computer simulation.

The memory module 1220 is for loading thereinto a model defining avirtual environment of the computer simulation. The virtual environmentdefines a plurality of zones comprising a first additive zone and asecond subtractive zone. The second subtractive zone is at leastpartially enclosed within the first additive zone. The image generatormodule 1232 adds a virtual contaminant over the first additive zone andremoves, at least partially, the virtual contaminant within the secondsubtractive zone leaving a remaining virtual contaminant in the firstadditive zone. The image generator module 1232 also renders an image fordisplay comprising the remaining virtual contaminant in the virtualenvironment using a visual texture of the virtual contaminant.

In the context of the illustrated example, the computer system 1200 mayfurther comprise an input instrument simulation module 1250 forreceiving control command inputs (e.g., manipulations from the traineeand/or the operator). The instrument simulation module 1250 may comprisephysical and/or logical representations of a simulated instrument module(simulated control panel or cockpit with logical and physicalinterfaces, etc.). The computer system 1200 may further comprise asimulation computing module 1234 for computing the control commandinputs in accordance with rules of the computer simulation (orsimulation code). The simulation computing module 1234 may be providedas a distinct module or as a portion, dedicated or not, of the processormodule 1230 as exemplarily illustrated on FIG. 1. The image generatormodule 1232 may, in response to the computing performed by simulationcomputing module 1234 and/or the processor module 1230 more generally,further modify the field of view for rendering a subsequent image fordisplay comprising the remaining virtual contaminant in the virtualenvironment.

The image generator module 1232 may remove, at least partially, thevirtual contaminant during the computer simulation, before each timeimage rendering for display is performed. The image generator module1232 may also add the virtual contaminant during the computersimulation, before each time removing, at least partially, the virtualcontaminant is performed. Alternatively, the image generator module 1232may add the virtual contaminant for the rendered scene at once, beforerendering the image for display is performed during the computersimulation (the removal being performed at once or upon each rendering).

In another optional embodiment, the image generator module 1232 may addthe virtual contaminant and may remove, at least partially, the virtualcontaminant for the rendered scene at once, before rendering the imagefor display being performed during the computer simulation.

The virtual environment may further define a plurality of additivepolygons within the first additive zone and the image generator module1232 may then add the virtual contaminant by performing a maximummathematical operation on the plurality of additive polygons to obtain avirtual contaminant image mask for the first additive zone. In thecontext of the present invention, polygons may be used to simplify imagerendering by having a number of surfaces (typically triangles)representing the visible outer skin of a 3D or 2D shape (e.g., ratherthan by having a much higher number of individual points). The use ofpolygons may also simplify the environment modeling (as explainedfurther below). Skilled persons will understand that othersimplifications may be applied to image rendering and/or environmentmodeling (in addition to or in lieu of the polygons) in the context ofthe present invention.

The virtual environment may also define a plurality of subtractivepolygons within the second subtractive zone and the image generatormodule 1232 may then remove the virtual contaminant by performing aminimum mathematical operation on the plurality of subtractive polygonsto obtain the remaining virtual contaminant in the virtual contaminantimage mask for the first additive zone. In one embodiment, the firstadditive zone and the second subtractive zone are both defined usingpolygons. In another embodiment, only the second subtractive zone isdefined using polygons and the first additive zone is defined usinganother technique. The plurality of additive polygons may furthercomprises linear polygons associated with a single pre-defined texture,tip polygons associated with two pre-defined textures and custompolygons associated with a plurality of arbitrary textures.

The image generator module 1232 may further render the image for displayby rendering the remaining virtual contaminant in the virtualcontaminant image mask by performing a multiply mathematical operationon the visual texture of the virtual contaminant and the virtualcontaminant image mask. The visual texture of the virtual contaminantmay further be mapped onto the plurality of additive polygons.

In an optional embodiment, the virtual environment may define pathswithin at least the second subtractive zone using vectors and the imagegenerator module 1232 may then remove the virtual contaminant byextrusion along the paths. The extrusion may be performed in 2D alongthe paths and the paths may further define at least one border forallowing smooth visual transition with one or more images neighboringthe paths.

The solution described herein may be used for rendering a 2D image ofthe virtual contaminants in a 3D scene and may be extrapolated torendering 3D shape (or a 2D projection of the 3D shape) representing thevirtual contaminant in the 3D scene. In this 3D exemplary context, theextrusion may be performed along a 3D path (e.g., leaving a variable“depth” of the virtual contaminants along its width).

FIG. 2 shows a flow chart of an exemplary a method 2000 for renderingvirtual contaminants on a rendered scene in a computer simulation inaccordance with the first set of embodiments exemplified above. Themethod 2000 comprises reading (2010) the model from a database (e.g.,the storage module 1400) or otherwise loading the model, e.g., from thememory module 1220). As previously mentioned, the model defines avirtual environment of the computer simulation. The virtual environmentdefines a plurality of zones comprising a first additive zone and asecond subtractive zone, the second subtractive zone being at leastpartially enclosed within the first additive zone. The method furthercomprises adding (2020) a virtual contaminant over the first additivezone, removing (2030), at least partially, the virtual contaminantwithin the second subtractive zone leaving a remaining virtualcontaminant in the first additive zone and rendering (2040) an image fordisplay comprising the remaining virtual contaminant in the virtualenvironment using a visual texture of the virtual contaminant.

The computer simulation may be a vehicle computer simulation and a fieldof view for rendering the image may be defined from a user's positionwithin a simulated vehicle as exemplified above. In that context, themethod may further comprise receiving control command inputs from aninput instrument simulation module, computing the control command inputsin accordance with rules of the computer simulation and, in response tothe computing, modifying the field of view for rendering a subsequentimage for display comprising the remaining virtual contaminant in thevirtual environment.

Removing, at least partially, the virtual contaminant may optionally beperformed, during the computer simulation, before each time imagerendering for display is performed. Adding the virtual contaminant may,as a complementary option, be performed, during the computer simulation,before each time removing, at least partially, the virtual contaminantis performed. Adding the virtual contaminant may alternatively beperformed for the rendered scene at once, before rendering the image fordisplay is performed during the computer simulation. Rendering the imagefor display may optionally be performed in an image generator modulehaving one or more dedicated graphical processing units.

In another optional embodiment, adding the virtual contaminant andremoving, at least partially, the virtual contaminant may be performedfor the rendered scene at once, before rendering the image for displayis performed during the computer simulation.

The virtual environment may further define a plurality of additivepolygons within the first additive zone. Adding the virtual contaminantwould then further comprise performing a maximum mathematical operationon the plurality of additive polygons to obtain a virtual contaminantimage mask for the first additive zone. The virtual environment may alsooptionally define a plurality of subtractive polygons within the secondsubtractive zone. Removing the virtual contaminant would then furthercomprise performing a minimum mathematical operation on the plurality ofsubtractive polygons to obtain the remaining virtual contaminant in thevirtual contaminant image mask for the first additive zone. Renderingthe image for display may thus comprise rendering the remaining virtualcontaminant in the virtual contaminant image mask by performing amultiply mathematical operation on the visual texture of the virtualcontaminant and the virtual contaminant image mask. The visual textureof the virtual contaminant may further be mapped onto the plurality ofadditive polygons.

The plurality of additive polygons may further comprise linear polygonsassociated with a single pre-defined texture, tip polygons associatedwith two pre-defined textures and custom polygons associated with aplurality of arbitrary textures.

In an optional embodiment, the virtual environment may define pathswithin at least the second subtractive zone using vectors and removingthe virtual contaminant may then be performed by extrusion along thepaths. The extrusion may be performed in 2D along the paths and thepaths may define at least one border for allowing smooth visualtransition with one or more images neighboring the paths.

Reference is now made to FIG. 1 with particular reference to a secondset of embodiments. In accordance with the second set of embodiments,the computer system 1200 is for modeling, in a virtual environment of acomputer simulation, virtual contaminants in a scene to be rendered. Inthe context of the second set of embodiments, the computer system 1200,while it may be able to do so, is not expected to run the computersimulation itself or at least not run the computer simulation at fullrate. In this exemplary context, the processing module 1230 is for,using a graphical user interface on the display device 1100, defining,in a model, a first additive zone of the scene over which a virtualcontaminant is to be added and defining, in the model, a secondsubtractive zone of the scene over which the virtual contaminant is tobe at least partially removed, the second subtractive zone being atleast partially enclosed within the first additive zone. The memorymodule 1220 is for storing the model, the model being made availablethrough the storage module 1400 for rendering the virtual contaminantson the scene in the computer simulation (e.g., in accordance with thefirst set of embodiments).

The processing module 1230 may further be for defining the firstadditive zone further by defining a plurality of additive polygonswithin the first additive zone to allow production of a virtualcontaminant image mask for the first additive zone. The processingmodule 1230 may also further be for defining the second subtractive zonefurther by defining a plurality of subtractive polygons within thesecond subtractive zone to allow determination of a remaining virtualcontaminant in the virtual contaminant image mask for the first additivezone and for associating a visual texture of the virtual contaminantoutside the model. For instance, the visual texture of the virtualcontaminant may be different at the time of image rendering and at thetime of modeling (or may be absent at the time of modeling). The visualtexture may thus be updated without changing the model. Thedetermination of the remaining virtual contaminant may be performed,during the computer simulation, by an image generator module of anothercomputer system (e.g., in accordance with the first set of embodiments)having predicted (or expected) processing capacities before each timeimage rendering for display is performed. As such, during the modeling,the polygons may be sized or otherwise defined in accordance with thepredicted processing capacities of the image generator module. Moregenerally, when polygons are not used, the first additive zone may bedefined in accordance with the predicted processing capacities of theimage generator module. As such, the computer simulation may be modeledconsidering that the image generator module having one or more dedicatedgraphical processing units will be rendering the scene images.

The plurality of additive polygons may comprise linear polygonsassociated, during the rendering, with a single pre-defined texture, tippolygons associated, during the computer simulation, with twopre-defined textures and custom polygons associated, at runtime, with aplurality of arbitrary textures. The plurality of subtractive polygonsmay also comprise linear polygons, tip polygons and custom polygons.

The processing module 1230 may also further be for defining the secondsubtractive zone further by defining paths within at least the secondsubtractive zone using vectors along which the virtual contaminant is tobe removed (e.g., by extrusion). The extrusion may be performed in 2D or3D along the paths and the processing module 1230 may further be for, inthe model, defining at least one border along the paths for allowingsmooth visual transition with one or more images neighboring the paths.

The computer simulation may be a vehicle computer simulation and a fieldof view for rendering the image is defined from a user's position withina simulated vehicle (as exemplified in the context of the first set ofembodiments). The processing module may also further be for launchingthe computer simulation in a preview mode and, in the preview mode, fora single image and considering the field of view, adding a virtualcontaminant over the first additive zone and removing, at leastpartially, the virtual contaminant within the second subtractive zoneleaving a remaining virtual contaminant in the first additive zone. Theprocessing module 1230 may also further be for, in the preview mode,rendering, at a rate lower than the expected rate of the computersimulation, images for display comprising the remaining virtualcontaminant in the virtual environment using a visual texture of thevirtual contaminant for display on the display device 1100.

During the preview mode, the same principal of rendering explained inthe context of the first set of embodiments may be applied. Morespecifically, the virtual environment may further define a plurality ofadditive polygons within the first additive zone. The processing module1230 may be further for adding the virtual contaminant further byperforming a maximum mathematical operation on the plurality of additivepolygons to obtain a virtual contaminant image mask for the firstadditive zone. The virtual environment may also define a plurality ofsubtractive polygons within the second subtractive zone and theprocessing module may then be further for removing the virtualcontaminant further by performing a minimum mathematical operation onthe plurality of subtractive polygons to obtain the remaining virtualcontaminant in the virtual contaminant image mask for the first additivezone. The processing module 1230 may yet further be for rendering theimage for display on the display device by rendering the remainingvirtual contaminant in the virtual contaminant image mask by performinga multiply mathematical operation on the visual texture of the virtualcontaminant and the virtual contaminant image mask.

FIG. 3 shows a method 3000, in accordance with the second set ofembodiments, for modeling, in the virtual environment of the computersimulation, virtual contaminants in a scene to be rendered. The method3000 comprises, in a model, defining (3010) a first additive zone of thescene over which a virtual contaminant is to be added, in the model,defining (3020) a second subtractive zone of the scene over which thevirtual contaminant is to be at least partially removed, the secondsubtractive zone being at least partially enclosed within the firstadditive zone and storing (3030) the model into a memory module forsubsequently rendering the virtual contaminants on the scene in thecomputer simulation.

In an optional embodiment, defining the first additive zone may furthercomprise defining a plurality of additive polygons within the firstadditive zone to allow production of a virtual contaminant image maskfor the first additive zone. Defining the second subtractive zone mayalso further comprise defining a plurality of subtractive polygonswithin the second subtractive zone to allow determination of a remainingvirtual contaminant in the virtual contaminant image mask for the firstadditive zone. The method may then further comprise associating a visualtexture of the virtual contaminant outside the model. The determinationof the remaining virtual contaminant may be performed, during thecomputer simulation, before each time image rendering for display isperformed.

The plurality of additive polygons may comprise linear polygonsassociated, during the rendering, with a single pre-defined texture, tippolygons associated, during the computer simulation, with twopre-defined textures and custom polygons associated, at runtime, with aplurality of arbitrary textures. The plurality of subtractive polygonsmay also comprise linear polygons, tip polygons and custom polygons.

Optionally, defining the second subtractive zone may further comprisedefining paths within at least the second subtractive zone using vectorsalong which the virtual contaminant is to be removed by extrusion. Theextrusion may be performed in 2D along the paths and the method mayfurther comprise, in the model, defining at least one border along thepaths for allowing smooth visual transition with one or more imagesneighboring the paths.

The computer simulation may be modeled considering that an imagegenerator module having one or more dedicated graphical processing unitswill be rendering the scene images.

The computer simulation may be a vehicle computer simulation and a fieldof view for rendering the image is defined from a user's position withina simulated vehicle. The method may then further comprise launching thecomputer simulation in a preview mode and, in the preview mode, for asingle image and considering the field of view, adding a virtualcontaminant over the first additive zone and removing, at leastpartially, the virtual contaminant within the second subtractive zoneleaving a remaining virtual contaminant in the first additive zone. Themethod may also further comprise, in the preview mode, rendering, at arate lower than the expected rate of the computer simulation, the singleimage for display comprising the remaining virtual contaminant in thevirtual environment using a visual texture of the virtual contaminantfor display on a display device. The virtual environment may define aplurality of additive polygons within the first additive zone and addingthe virtual contaminant may then further comprise performing a maximummathematical operation on the plurality of additive polygons to obtain avirtual contaminant image mask for the first additive zone. The virtualenvironment may also define a plurality of subtractive polygons withinthe second subtractive zone and removing the virtual contaminant maythen further comprise performing a minimum mathematical operation on theplurality of subtractive polygons to obtain the remaining virtualcontaminant in the virtual contaminant image mask for the first additivezone. Rendering the image for display may yet further comprise renderingthe remaining virtual contaminant in the virtual contaminant image maskby performing a multiply mathematical operation on the visual texture ofthe virtual contaminant and the virtual contaminant image mask.

The processor module 1230 may represent a single processor with one ormore processor cores or an array of processors, each comprising one ormore processor cores. The memory module 1220 may comprise various typesof memory (different standardized or kinds of Random Access Memory (RAM)modules, memory cards, Read-Only Memory (ROM) modules, programmable ROM,etc.). The network interface module 1210 represents at least onephysical interface that can be used to communicate with other networknodes. The network interface module 1210 may be made visible to theother modules of the computer system 1200 through one or more logicalinterfaces. The actual stacks of protocols used by the physical networkinterface(s) and/or logical network interface(s) of the networkinterface module 1210 do not affect the teachings of the presentinvention. The variants of processor module 1230, memory module 1220,network interface module 1210 and storage devices module 1400 usable inthe context of the present invention will be readily apparent to personsskilled in the art. Likewise, even though explicit mentions of thememory module 1220 and/or the processor module 1230 are not madethroughout the description of the present examples, persons skilled inthe art will readily recognize that such modules are used in conjunctionwith other modules of the computer system 1200 to perform routine aswell as innovative steps related to the present invention.

A method is generally conceived to be a self-consistent sequence ofsteps leading to a desired result. These steps require physicalmanipulations of physical quantities. Usually, though not necessarily,these quantities take the form of electrical or magnetic/electromagneticsignals capable of being stored, transferred, combined, compared, andotherwise manipulated. It is convenient at times, principally forreasons of common usage, to refer to these signals as bits, values,parameters, items, elements, objects, symbols, characters, terms,numbers, or the like. It should be noted, however, that all of theseterms and similar terms are to be associated with the appropriatephysical quantities and are merely convenient labels applied to thesequantities. The description of the present invention has been presentedfor purposes of illustration but is not intended to be exhaustive orlimited to the disclosed embodiments. Many modifications and variationswill be apparent to those of ordinary skill in the art. The embodimentswere chosen to explain the principles of the invention and its practicalapplications and to enable others of ordinary skill in the art tounderstand the invention in order to implement various embodiments withvarious modifications as might be suited to other contemplated uses.

What is claimed is:
 1. A method for rendering virtual contaminants on arendered scene in a computer simulation comprising: reading a model froma database, the model defining a virtual environment of the computersimulation, the virtual environment defining a plurality of zonescomprising a first additive zone and a second subtractive zone, thesecond subtractive zone being at least partially enclosed within thefirst additive zone; adding a virtual contaminant over the firstadditive zone; removing, at least partially, the virtual contaminantwithin the second subtractive zone leaving a remaining virtualcontaminant in the first additive zone; and rendering an image fordisplay comprising the remaining virtual contaminant in the virtualenvironment using a visual texture of the virtual contaminant.
 2. Themethod of claim 1, wherein the computer simulation is a vehicle computersimulation and a field of view for rendering the image is defined from auser's position within a simulated vehicle.
 3. The method of claim 2,further comprising: receiving control command inputs from an inputinstrument simulation module; computing the control command inputs inaccordance with rules of the computer simulation; and in response to thecomputing, modifying the field of view for rendering a subsequent imagefor display comprising the remaining virtual contaminant in the virtualenvironment.
 4. The method of claim 3, wherein removing, at leastpartially, the virtual contaminant is performed, during the computersimulation, before each time image rendering for display is performed.5. The method of claim 4, wherein adding the virtual contaminant isperformed, during the computer simulation, before each time removing, atleast partially, the virtual contaminant is performed.
 6. The method ofclaim 4, wherein adding the virtual contaminant is performed for therendered scene at once, before rendering the image for display isperformed during the computer simulation.
 7. The method of claim 5,wherein rendering the image for display is performed in an imagegenerator module having one or more dedicated graphical processingunits.
 8. The method of claim 1, wherein adding the virtual contaminantand removing, at least partially, the virtual contaminant are performedfor the rendered scene at once, before rendering the image for displayis performed during the computer simulation.
 9. The method of claim 7,wherein the virtual environment defines a plurality of additive polygonswithin the first additive zone, wherein adding the virtual contaminantfurther comprises performing a maximum mathematical operation on theplurality of additive polygons to obtain a virtual contaminant imagemask for the first additive zone.
 10. The method of claim 9, wherein theplurality of additive polygons comprises linear polygons associated witha single pre-defined texture, tip polygons associated with twopre-defined textures and custom polygons associated with a plurality ofarbitrary textures.
 11. The method of claim 1, wherein the virtualenvironment defines a plurality of subtractive polygons within thesecond subtractive zone, wherein removing the virtual contaminant isperformed, during the computer simulation, before each time imagerendering for display is performed and further comprises performing aminimum mathematical operation on the plurality of subtractive polygonsto obtain the remaining virtual contaminant in the virtual contaminantimage mask for the first additive zone.
 12. The method of claim 11,wherein rendering the image for display comprises rendering theremaining virtual contaminant in the virtual contaminant image mask byperforming a multiply mathematical operation on the visual texture ofthe virtual contaminant and the virtual contaminant image mask.
 13. Themethod of claim 11, wherein the visual texture of the virtualcontaminant is mapped onto the plurality of additive polygons.
 14. Themethod of claim 1, wherein the virtual environment defines paths withinat least the second subtractive zone using vectors, wherein removing thevirtual contaminant is performed by extrusion along the paths.
 15. Themethod of claim 14, wherein the extrusion is performed in 2D along thepaths and the paths define at least one border for allowing smoothvisual transition with one or more images neighboring the paths.
 16. Acomputer system for performing a computer simulation in which virtualcontaminants are rendered on a rendered scene of the computersimulation, the computer system comprising: a memory module for loadingthereinto a model defining a virtual environment of the computersimulation, the virtual environment defining a plurality of zonescomprising a first additive zone and a second subtractive zone, thesecond subtractive zone being at least partially enclosed within thefirst additive zone; and an image generator module for: adding a virtualcontaminant over the first additive zone; removing, at least partially,the virtual contaminant within the second subtractive zone leaving aremaining virtual contaminant in the first additive zone; and renderingan image for display comprising the remaining virtual contaminant in thevirtual environment using a visual texture of the virtual contaminant.17. The computer system of claim 16, wherein the computer simulation isa vehicle computer simulation and a field of view for rendering theimage is defined from a user's position within a simulated vehicle. 18.The computer system of claim 17, further comprising: an input instrumentsimulation module for receiving control command inputs; a simulationcomputing module for computing the control command inputs in accordancewith rules of the computer simulation; and wherein the image generatormodule, in response to the computing, is further for modifying the fieldof view for rendering a subsequent image for display comprising theremaining virtual contaminant in the virtual environment.
 19. Thecomputer system of claim 18, wherein the image generator module removes,at least partially, the virtual contaminant during the computersimulation, before each time image rendering for display is performed.20. The computer system of claim 19, wherein the image generator moduleadds the virtual contaminant during the computer simulation, before eachtime removing, at least partially, the virtual contaminant is performed.21. The method of computer system 20, wherein the image generator moduleadds the virtual contaminant for the rendered scene at once, beforerendering the image for display is performed during the computersimulation.
 22. The computer system of claim 21, wherein the imagegenerator module comprises one or more dedicated graphical processingunits.
 23. The computer system of claim 16, wherein the image generatormodule adds the virtual contaminant and removes, at least partially, thevirtual contaminant for the rendered scene at once, before rendering theimage for display being performed during the computer simulation. 24.The computer system of claim 16, wherein the virtual environment definesa plurality of additive polygons within the first additive zone, whereinthe image generator module adds the virtual contaminant by performing amaximum mathematical operation on the plurality of additive polygons toobtain a virtual contaminant image mask for the first additive zone. 25.The computer system of claim 24, wherein the plurality of additivepolygons comprises linear polygons associated with a single pre-definedtexture, tip polygons associated with two pre-defined textures andcustom polygons associated with a plurality of arbitrary textures. 26.The computer system of claim 1, wherein the virtual environment definesa plurality of subtractive polygons within the second subtractive zone,wherein the image generator module removes, during the computersimulation and before each time image rendering for display isperformed, the virtual contaminant by performing a minimum mathematicaloperation on the plurality of subtractive polygons to obtain theremaining virtual contaminant in the virtual contaminant image mask forthe first additive zone
 27. The computer system of claim 26, wherein theimage generator module renders the image for display by rendering theremaining virtual contaminant in the virtual contaminant image mask byperforming a multiply mathematical operation on the visual texture ofthe virtual contaminant and the virtual contaminant image mask.
 28. Thecomputer system of claim 26, wherein the visual texture of the virtualcontaminant is mapped onto the plurality of additive polygons by theimage generator module.
 29. The computer system of claim 16, wherein thevirtual environment defines paths within at least the second subtractivezone using vectors, wherein the image generator module removes thevirtual contaminant by extrusion along the paths.
 30. The computersystem of claim 29, wherein the extrusion is performed in 2D along thepaths and the paths define at least one border for allowing smoothvisual transition with one or more images neighboring the paths.